The present invention relates to check valves, and more particularly, to a check valve which is specifically adapted for use with a medical syringe. The check valve may be used to close a fluid conduit or container. The syringe may be inserted into the valve to withdraw fluid from the conduit or container.
In providing medical treatment to patients, it is often necessary to administer medications and other fluids to the patient using a syringe equipped with a needle. To prevent contamination, the needle should not be installed upon the syringe until immediately before insertion of the needle into the patient's body. As a result, it is preferred that the syringe not be filled by inserting the needle tip into the container of medication of other fluid. To accomplish this, the syringe is filled without the needle or other attachment mounted at its distal end.
Fluid is often withdrawn into the syringe from a bulk container. In large institutions such as hospitals a number of syringes are often filled by a single technician working in a central medicine supply area. In such environments, the fluid may be held within an elevated container, with a conduit extending from the container to the work area. The conduit is closed by a valve which normally prevents fluid from emerging from the conduit. Fluid may be drawn into the syringe upon connnecting the syringe with the valve.
One common type of valve for use in such a manner is a conventional stopcock. Such a valve includes a port for connection to the fluid supply and a port which is selectively connectible to the distal end of a syringe to be filled. A rotary valving portion is disposed in the flow path, and is movable between an open position and a closed position. After a syringe has been connected to the valve, the rotary portion is turned, typically via a handle, to permit fluid flow.
Because such a valve includes moving parts, great care must be taken in manufacturing the valve. More importanting, since the valving mechanism, i.e., the rotary portion, is mounted internally, the valve cannot be effectively cleaned.
A second type of check valve which could be used for closing such a fluid supply conduit is shown in U.S. Pat. No. 3,831,629, issued Aug. 27, 1974 to Mackal et al. Such a valve is often used in the inflation of urethral catheters. The valve includes a sleeve-like body including a rear portion and a relatively narrow forward portion, the junction between the portions defining a sealing surface. A plug-like valve element is disposed within the body, and is urged forward by an elastomeric rear portion connecting the valve element with the valve body. The element is held in contact with the sealing surface, thereby closing the fluid conduit. When the distal end of the syringe is inserted into the forward portion of the valve body, it contacts the valve element. This in turn moves the element rearwardly, opening a fluid passage around the valve element.
One disadvantage with the check valve disclosed in Mackal et al is the tortuous path which the fluid must follow as it passes around the valve element. For example, where the fluid is blood, the red blood cells can be damaged as they bump against each other and the valve elements and valve body walls while moving around the elements within the valve. Even in the case of a medications, the pressure drop as the fluid passes the valve element may introduce air into the fluid or may otherwise detrimentally agitate the solution.
What is needed, therefore, is a check valve for use in conjunction with a syringe for withdrawing fluids from a supply container. Such a valve should eliminate the problem noted above by providing for easy cleaning of the valve, and by defining a straight flow path for the fluid with no appreciable pressure drop. The valve should be capable of quickly be resealed, and should be sufficiently inexpensive that the valve assembly is disposable.